Strange dynamic topography in global data assimilation model

[lixinyv]

Hi,

I’m using ASPECT to develop a global mantle convection model with data assimilation. However, the dynamic topography looks a little strange. There are 40 km depth continental crust and 8 km depth oceanic crust in my model. Therefore, the elevation of continents and oceans should be similar to the present-day topography, like previous data assimilation models using CitcomS.

However, in my model, the topography looks pretty strange. Both the elevation of continents and oceans are much higher than the real situation. Especially for the mid-ocean ridges, the elevation could reach 1800m above the sea level. Some snapshots are as follows.

I’d like to know if there is someway to correct the topography.

Thanks a lot!
Xinyu Li

[Shangxin-Liu]

Hi Xinyu,

Thanks for posting your material. First of all, I don’t think there is an issue of the dynamic topography calculation in ASPECT. We have systematically benchmarked the dynamic topography kernel in 3D spherical shell geometry for ASPECT. Details can be found here: https://academic.oup.com/gji/article/217/1/650/5290318 .

As you can see from the equations to calculate dynamic topography, it depends on both buoyancy and rheological structures. Therefore, in order to debug your problem more efficiently, can you share more details about your density and viscosity structures? For example, how strong is your lithosphere and do you add weak plate boundaries into your models? What are the shallow density structures in your models?

If you think it is ok, a prm file of one of your test cases will be particularly useful to help you.

Best,
Shangxin

[lixinyv]

Hi Shangxin,

Thanks for your reply! The version of ASPECT I’m using is 2.6-pre. The following are the details of my model. First, the oceanic plates are divided into two layers: 8 km oceanic crust with a density of 3000 kg/m3 and 8km depth to 80 km depth oceanic lithospheric mantle. For the continental plates, there are 3 layers: 20 km upper crust, 20 km lower crust, and 120 km continental lithosphere mantle. Due to the distribution of oceans and continents, the topography in my model includes both dynamic topography and isostatic topography. The material subsection is visco plastic. Please check the parameter file attached.

For the material names, C1: oceanic crust, C2: upper continental crust, C3: lower continental crust, C4: continental lithospheric mantle, C5: oceanic lithospheric mantle, C6: weak zones, C7: LLSVPs

test_for_data_assimilation.prm (12.6 KB)

Thanks a lot!
Xinyu Li